Laser welding methods and structures and control therefor including welded inkjet printheads

ABSTRACT

In a system for laser welding work pieces along a collapsing weld interface, methods and apparatus include providing welding pads and/or stop projections on either or both of the work pieces to control the manner or amount of collapse. Preferably, the stop projections exist a separation distance from the weld interface while the welding pads exist at and form a portion of the weld interface. Buffers are taught between the weld interface and stop projection. The work pieces may comprise inkjet printhead lids and bodies. In another aspect, the invention teaches methods of laser welding inkjet printhead lids and bodies according to whether the inkjet printhead body embodies a mono or color ink body type and especially includes selective control of one or more laser light sources to illuminate the inkjet printhead lid in a specific pattern of light.

This application is a divisional application of U.S. patent applicationSer. No. 10/299,792 filed on Nov. 19, 2002 now U.S. Pat. No. 6,974,207,entitled “Laser Welding Methods and Structures and Control ThereforIncluding Welding Inkjet Printheads.”

FIELD OF THE INVENTION

The present invention relates to laser welding first and second workpieces. In one aspect, it relates to stop projections and welding padson either or both of the first and second work pieces for controlling amanner and amount of collapse in a laser weld joint. In another aspect,it relates to controlling a manner of welding according to a structuretype of the first or second work piece. The work pieces may specificallyembody inkjet printhead lids and bodies used in inkjet printing.

BACKGROUND OF THE INVENTION

The art of laser welding is relatively well known. In general, withreference to FIG. 1, first and second work pieces, embodied as an upperwork piece 100 laid on a lower work piece 120 along a weld interface180, become welded to one another by way of an irradiated beam 140 oflaser light. As is known, the beam 140 passes through the upper workpiece, which is laser light absorbent, where it gets absorbed by thelower work piece, which is opaque to laser light. As the beamirradiates, the weld interface heats up and causes the bottom surface ofthe upper work piece and the upper surface of the lower work piece tomelt and meld together. Upon cooling, a weld joint remains. An opticalpath between a laser light source (not shown) and the to-be-welded workpieces may include a lens 160, for proper focusing, or other opticalelements, such as mirrors, fiber optic strands, scanning structures orother. A clamping device (not shown) typically provides a pressingengagement of the work pieces to maintain relative positioning and goodsurface contact during welding. Those skilled in the art also know thatthe beam may weld as an advancing beam of light (embodied as either thebeam of light moving relative to stationary work pieces, work piecesmoving relative to a stationary beam or both moving relative to oneanother) during contour welding or as a simultaneous weld (embodied asan entirety of a weld interface being welded at the same time by a lightbeam with substantially no movement of the work pieces or beam).

As is apparent in FIG. 1, the two work pieces 100, 120 comprisegenerally uniformly shaped and flat structures with a relatively lengthyweld interface. Thus, under heat and pressure during welding, the weldjoint along the weld interface 180 does not suffer any appreciablecollapse.

With reference to FIGS. 2A and 2B, however, sometimes the work pieces donot embody uniformly shaped and flat structures as representativelyshown with a to-be-welded lid 200 and container 220, nor do they alwayshave a lengthy weld interface between the to-be-welded surfaces 210,212. In such instances, when heat and pressure become applied duringwelding, the weld joint 240 adversely suffers from bowing effects orother. Moreover, sometimes the work pieces additionally contain a cornerregion 250 that prevents sufficient heating of the weld interface whichfurther exacerbates the bowing condition. Often times bowing leads toundesirable manifestations, such as stress cracks.

Accordingly, a need exists in the laser welding arts for efficaciouslylaser welding two work pieces despite the work pieces embodyingnon-uniformly shaped or flat structures and/or having relatively smallor short weld interfaces.

Regarding the technology of inkjet printing, it too is relatively wellknown. In general, an image is produced by emitting ink drops from aninkjet printhead at precise moments such that they impact a printmedium, such as a sheet of paper, at a desired location. The printheadis supported by a movable print carriage within a device, such as aninkjet printer, and is caused to reciprocate relative to an advancingprint medium and emit ink drops at such times pursuant to commands of amicroprocessor or other controller. The timing of the ink drop emissionscorresponds to a pattern of pixels of the image being printed. Otherthan printers, familiar devices incorporating inkjet technology includefax machines, all-in-ones, photo printers, and graphics plotters, toname a few.

A conventional thermal inkjet printhead includes access to a local orremote supply of color or mono ink, a heater chip, a nozzle or orificeplate attached to the heater chip, and an input/output connector, suchas a tape automated bond (TAB) circuit, for electrically connecting theheater chip to the printer during use. The heater chip, in turn,typically includes a plurality of thin film resistors or heatersfabricated by deposition, masking and etching techniques on a substratesuch as silicon.

To print or emit a single drop of ink, an individual heater is uniquelyaddressed with a small amount of current to rapidly heat a small volumeof ink. This causes the ink to vaporize in a local ink chamber (betweenthe heater and nozzle plate) and be ejected through and projected by thenozzle plate towards the print medium.

During manufacturing of the printheads, a printhead body gets stuffedwith a back pressure device, such as a foam insert, and saturated withmono or color ink. A lid adheres or welds to the body via ultrasonicvibration. Ultrasonic welding, however, has often cracked the heaterchip, introduced and entrained air bubbles in the ink and compromisedoverall printhead integrity. Adhering has an impractically long curetime.

Even further, as demands for higher resolution and increased printingspeed continue, heater chips are often engineered with more complex anddenser heater configurations which raises printhead costs. Thus, asprintheads evolve, a need exists to control overall costs, despiteincreasing heater chip costs, and to reliably and consistentlymanufacture a printhead without causing cracking of the ever valuableheater chip.

SUMMARY OF THE INVENTION

The above-mentioned and other problems become solved by applying theprinciples and teachings associated with the hereinafter described laserwelding methods and structures and control therefor. In a system forlaser welding work pieces along a collapsing weld interface, theinvention teaches methods and apparatus including providing welding padsand/or stop projections on either or both of the work pieces to controlthe manner or amount of the collapse. The welding pads and the clearancebeside them prevent the prior art problem of bowed weld joints. The stopprojections impede or stop collapse from occurring beyond a desireddistance during welding.

In a preferred embodiment, the stop projections exist a separationdistance from the weld interface while the welding pads exist at andform a portion of the weld interface. Varieties of buffers are alsotaught between the weld interface and stop projection to prevent thestop projections from acquiring too much heat. In still anotherembodiment, the work pieces comprise inkjet printhead lids and bodieswith the welding pads and/or stop projections existing on either orboth.

Since mono ink and color ink inkjet printhead bodies require welds atdifferent locations and since a manufacturer would suffer inconvenienceif required to retool a laser welding apparatus when switchingmanufacturing from mono to color bodies, the invention further disclosesmethods of selectively controlling laser light according to whether theinkjet printhead body embodies a mono or color ink type. Preferably,laser light and laser power intensity becomes selectively controlled toilluminate specific patterns of light according to the actual inkjetprinthead body type requiring welding. The invention even contemplatescontrol for one or more laser light sources.

Still further, the invention discloses inkjet printers that contain thelaser welded printheads.

These and other embodiments, aspects, advantages, and features of thepresent invention will be set forth in the description which follows,and in part will become apparent to those of ordinary skill in the artby reference to the following description of the invention andreferenced drawings or by practice of the invention. The aspects,advantages, and features of the invention are realized and attained bymeans of the instrumentalities, procedures, and combinationsparticularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view in accordance with the prior art of twosubstantially uniformly shaped and flat work pieces being laser weldedtogether;

FIG. 2A is a diagrammatic view in accordance with the prior art of twonon-uniformly shaped work pieces requiring laser welding;

FIG. 2B is a diagrammatic view in accordance with the prior art of aweld joint after the work pieces of FIG. 2A have undergone laserwelding;

FIG. 3A is a diagrammatic view in accordance with the teachings of thepresent invention of a to-be-welded welding pad;

FIG. 3B is a diagrammatic view in accordance with the teachings of thepresent invention of the to-be-welded welding pad of FIG. 3A during alaser welding operation;

FIG. 3C is a diagrammatic view in accordance with the teachings of thepresent invention of a weld joint that remains after laser welding thewelding pad of FIG. 3B;

FIG. 3D is a diagrammatic view in accordance with the teachings of thepresent invention of a plurality of to-be-welded welding pads;

FIG. 3E is a diagrammatic view in accordance with the teachings of thepresent invention of an alternate embodiment of a to-be-welded weldingpad;

FIG. 3F is a diagrammatic view in accordance with the teachings of thepresent invention of an alternate embodiment of a plurality ofto-be-welded welding pads;

FIG. 4A is a diagrammatic view in accordance with the teachings of thepresent invention of a stop projection that impedes or stops collapseduring a laser welding operation;

FIG. 4B is a diagrammatic view in accordance with the teachings of thepresent invention of the stop projection of FIG. 4A after laser weldingof the work pieces;

FIGS. 4C is a diagrammatic view in accordance with the teachings of thepresent invention of an alternate embodiment of a stop projection;

FIG. 5 is a perspective view in accordance with the teachings of thepresent invention of a buffer between a stop projection and a weldinterface;

FIG. 6 is a perspective view in accordance with the teachings of thepresent invention of an alternate embodiment of a buffer between a stopprojection and a weld interface;

FIG. 7 is a perspective view in accordance with the teachings of thepresent invention of an inkjet printhead having a lid and body laserwelded together;

FIG. 8 is a perspective view in accordance with the teachings of thepresent invention of an inkjet printer for housing an inkjet printheadhaving a laser welded lid and body;

FIG. 9A is a diagrammatic top view of a surface of a mono inkjetprinthead body to be laser welded;

FIG. 9B is a diagrammatic top view of a surface of a color inkjetprinthead body to be laser welded;

FIG. 10A is a diagrammatic view of a bank of laser beam fiber opticbundles controlled for laser welding the mono inkjet printhead body ofFIG. 9A;

FIG. 10B is a diagrammatic view of another bank of laser beam fiberoptic bundles controlled, together with the bank of laser beam fiberoptic bundles of FIG. 10A, for laser welding the color inkjet printheadbody of FIG. 9B;

FIG. 11A is a diagrammatic view of a first embodiment of a laser weldingstructure for controlling the banks of laser beam fiber optic bundles ofFIGS. 10A and 10B during a welding operation of an inkjet printhead lidand body; and

FIG. 11B is a diagrammatic view of a second embodiment of a laserwelding structure for controlling the banks of laser beam fiber opticbundles of FIGS. 10A and 10B during a welding operation of an inkjetprinthead lid and body.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings that form a part hereof,and in which is shown by way of illustration, specific embodiments inwhich the inventions may be practiced. These embodiments are describedin sufficient detail to enable those skilled in the art to practice theinvention, and it is to be understood that other embodiments may beutilized and that process or other changes may be made without departingfrom the scope of the present invention. The following detaileddescription is, therefore, not to be taken in a limiting sense, and thescope of the present invention is defined only by the appended claimsand their equivalents.

In accordance with the present invention, we hereinafter describewelding pads and stop projections on either or both of first and secondwork pieces for controlling a manner and amount of collapse in a laserweld joint despite the work pieces embodying non-uniformly shaped orflat structures and/or having relatively small or short weld interfaces.In other aspects, we describe controlling a manner of welding accordingto a structure type of the first or second work piece and, in allembodiments, the work pieces may specifically embody inkjet printheadlids and bodies used in inkjet printing.

With reference to FIGS. 3A-3C, the invention teaches a welding pad 346on one of the to-be-welded first and second work pieces 300, 320 thatsubstantially prevents bowing of a weld joint 330 because of arelatively small or short weld interface despite the presence of acorner region 350 and a relatively small or short weld interface. Asshown, the welding pad 346 extends a distance d1 from a planar surface342 of the second work piece 320 and a top 344 of the welding pad and anundersurface 302 of the first work piece, when contacted with oneanother (FIG. 3B), form a weld interface between positions 366 and 364.During welding, heat and pressure cause the weld interface to collapsebut not so much as to have a bowed weld joint as in the prior art.

More specifically, a beam of laser light 340 transits the first workpiece 300, which is transparent to laser light, to weld the first andsecond work pieces together at the weld interface. Since the second workpiece is laser light absorbent, as the beam 340 passes through the firstwork piece it gets absorbed by the lower work piece and heats the weldinterface. Eventually the materials of the first and second work piece,including the material of the welding pad, melt and meld together.Pressure, indicated by force line F from a clamping or pressing device(not shown), forces the welding pad to collapse. Upon cooling, a weldjoint 330 (FIG. 3C) exists that improves the bowing of the prior art.Although not shown, other forces likely oppose force line F fromunderneath and normal to a bottom surface of the second work piece asthe bottom surface rests on a platform, for example, during welding.

Regarding the optical system of the laser welding structure, a lens 360focuses the beam 340 to the welding pad during welding but those skilledin the art should appreciate that we greatly simplified the optical pathand an actual optical path may exclude the lens, replace the lens oradditionally include other optical structures such as mirrors, fiberoptic strands, laser scanning devices (e.g., rotating multi-facetedmirrors), other lenses or other. Preferably, the laser beam originatesfrom a laser source such as a laser diode or a solid state laser.

Still further, those skilled in the art should appreciate the weldingpad of the present invention provides an extra source of weldablematerial at the weld interface which contributes to resisting thecollapsing force thereby controlling the collapse from becoming a bowedweld joint. As such, when the dimensions and material properties of thework pieces are fixed and the laser welding structure has fixedparameters, such as wavelength, time on, power, force, etc., the amountof collapse is generally dictated by the dimensions of the welding pad346. Thus, the invention contemplates variously sized welding paddimensions.

In one specific embodiment (FIG. 3D), presented merely as representativeand not restrictive, the welding pad 346 has height d2 of about 0.4 mmand width of about 0.8 mm. Its length dimension, into or away from thepaper, is generally dictated by the length dimension of the second workpiece, into or away from the paper, and preferably shares such length.It also preferably shares the composition of the second work piece andin one embodiment comprises a plastic having a polyphenolynether pluspolystyrene blend.

Regarding further compositions, the first work piece 300 (inkjetprinthead lid) is preferably substantially entirely transparent and maycomprise a polyphenylene ether plus polystyrene (PPE/PS) blend such asthat found in Noryl brand SE1 resin. Compositions of the second workpiece 320 (inkjet printhead body), on the other hand, include, but arenot limited to, general purpose polystyrene, high impact polystyrene,such as styrene-butadiene copolymers (CBC), styrene-acrylic copolymers(SMMA). Still others include polyesters and polyester blends includingpolyethylene terephthalate (PET), polybutylene terephthalate (PBT), aswell as blends of these plus polycarbonate (PC), acrylonitrile styreneacrylic (ASA) or other resins or other. When the second work piece is ofa PET composition, preferred first work piece component compositionsinclude the foregoing and/or may additionally include copolyesters,glycol modified PET (PETG), glycol modified polycyclohexylenemethyleneterephthalate (PCTG), and acid modified PCT (PCTA) or other. Suitablewelds have also been found when the first work piece 300 comprisesmaterials having low loading levels of glass fiber such as natural PET(15% glass fiber) or blends of polyester types. Still other compositionsinclude PC/PCTG, PC/PBT, PC/PET, PBT/PETG, PET/PBT, although thesesometimes require laser power adjustment when welding to polyesterinkjet printhead bodies. In still other embodiments, PBT/ASA was foundto join to materials such as styrene methyl methacrylate (SMMA), andstyrene acrylonitrile (SAN). One PET/PBT blend surprisingly formed goodbonds with SMMA, clear ABS, ABS and methacrylate ABS (MABS). Thematerials discussed above are summarized in Appendix 1 (body materialscorrespond to the second work piece 320 while the lid materials refersto the first work piece 300). Bear in mind, compatibility with inks canalso be considered when selecting suitable compositions when weldinginkjet printhead lids to inkjet printhead bodies.

The welding pad may become formed on the work piece through any varietyof processing steps. Preferably, it gets formed integrally on the workpiece during formation of the work piece. In the instance when the workpiece constitutes a plastic, the welding pad and work piece can becomeformed as a result of any of the well known injection molding processes.

As further seen in FIG. 3D, those skilled in the art should appreciatethat more than one welding pad can exist on a work piece at one time. Inthis embodiment, a second welding pad 356 exists a vertically spaceddistance d6 above the welding pad 346 and has height d4 and width d5dimensions of about 0.4 mm and 0.8 mm respectively. A horizontaldistance d7 exists between the two welding pads in an amount of about0.7 mm.

Even further, those skilled in the art should appreciate that while thefigures depict welding pad(s) on the second work piece, a welding padmay also exist on the first work piece 300. As shown, a welding pad 376has a height d8 of about 0.75 mm and a width of about 2 mm. Like theother welding pads 346, 356, its length dimension generally follows thelength of its work piece.

In other embodiments, a welding pad may exist exclusively on the firstwork piece instead of the second work piece. FIG. 3E shows such anembodiment as a welding pad 386 extending some distance from a workpiece 300. In FIG. 3F, the invention contemplates that both work pieces300, 320 have welding pads 346, 386 and their relative positioning issuch that side surfaces 387, 347 exist adjacent to one another whencontacted or brought near one another before welding. It should also benoted that the welding pad 346 has a surface 348 opposite the surface347 that exists substantially flush with a surface 349 of the secondwork piece. In contrast, the welding pad 387 embodies a mid-mountstructure, i.e., it does not existing at or near a terminal end 353 ofthe work piece 300. Thus, both mid-mount and terminal end locatedwelding pads are embraced herein.

While the invention has shown various welding pad embodiments, stillfurther examples exist that can provide the advantage of the presentinvention. For example, the welding pads may embody shapes other thanrectangular masses, such as ovals, circles, semicircles, polygons,curved, irregular or other. Pluralities of fractional welding pads mayexist in close proximity to one another that together represent one ofthe welding pads shown. Still further, the welding pads may buttress thecorner region 250 or exist flush with surface 349, as shown in FIG. 3F,or at any position along the surface 342 or 313.

With reference to FIGS. 4A and 4B, in another aspect of the invention, astop projection 446 extends a distance d10 from a first work piece 400to control a distance of collapse between two to-be-welded work pieces400, 420. As shown, a weld interface exists when undersurface 402 of thefirst work piece contacts a top 444 of the second work piece betweenpositions 466 and 464 before welding. When contacted, a terminal end 447of the stop projection exists a distance d11 minus d12 above a surface442 of the second work piece. During welding, a beam of laser lightpasses through the first work piece 400 and heats the weld interface.Then, in combination with pressure, collapses the weld interface(especially collapsing the second work piece 420, between positions 464and 467, downward towards surface 442). The distance of collapse,however, becomes limited by the stop projection, namely the terminal end447, impacting or contacting the surface 442 of the second work piece.

After welding, the weld interface cools and becomes a weld joint 471. Ina preferred embodiment, the stop projection 446 exists a separationdistance d13 from the weld interface/joint defined between a terminalend 472 of the weld interface or weld join to a position 473 where thestop projection extends from the first work piece.

With reference to FIG. 4C, those skilled in the art should appreciatethat the stop projection 446 could alternatively exist exclusively onthe other work piece, second work piece 420. Then, during the heat andpressure of welding, a region 425 of the second work piece collapses inthe direction of arrow C until a surface 423 impacts or otherwisecontacts a surface 419 of the stop projection 446. In still otherembodiments, pluralities of stop projections could exist on a singlework piece or singles or pluralities could exist on both work pieces atthe same time.

In FIG. 5, a buffer 511 exists between the weld interface (whereundersurface 502 of the first work piece 500 contacts a top 544 of thesecond work piece 520 between positions 566 and 564) and the stopprojection 546. Such buffer, during welding, limits the amount of heat,thus the amount of melting, developed in the stop projection 546. Inthis manner, the structural integrity of the stop projection remainsintact and more sturdily resists the collapse and maintains structuralsupport for the weld joint during cooling. The buffer 511 may assume anyform including a rectangular cross-section cut in work piece 500 asshown. FIG. 6 differs from FIG. 5 only in the shape of the buffer 611.Preferably, buffer 611 limits an amount of laser light that arrives atthe stop projection 646 during welding, in turn, limiting heat andmelting.

Like the welding pads previously described, the stop projectionspreferably become formed of the same composition and at the same time asthe work piece on which they exist and do so under any of the well knowninjection molding processes. One preferred composition includespolyphenylene ether plus polystyrene.

Those skilled in the art should appreciate that the invention embracesall other shapes of buffers and even contemplates the addition of asubstance between the weld interface and the stop projection, thesubstance preferably having non-conductive heat and/or non-transmittanceof light properties.

As described herein, all embodiments have included a first work pieceembodied as a laser light transparent material and a second work pieceembodied as a laser light absorbing material. The transparency oropaqueness of theses structures, however, does not mean that 100% laserlight gets transmitted or blocked. The transparency and opacity is onlyrequired to allow enough light to transit the first work piece and getabsorbed by the second work piece to form an appropriate laser weld. Apreferred satisfactory rate of transmission for the first work pieceincludes rates above about 50%. A more preferred rate includes ratesabove about 80%. Those skilled in the art know that numerous parameterscontribute to the rate of transmission and include, among others, laserwavelength, incident angle of the laser beam, surface roughness of thework piece, temperature of the work pieces, thickness/dimensions of thework piece, composition of the work piece and, in the instance when thework pieces comprise plastics, additives such as flame retardants,plasticizers, fillers and colorants.

Since the to-be-welded work pieces of the present invention can embodyinkjet printhead lids and bodies, in FIGS. 7 and 8 we describe otherfunctional aspects of an inkjet printhead and the printer that usesthem. In particular, with reference to FIG. 7, a printhead of thepresent invention is shown generally as 101. The printhead 101 has ahousing 127 formed of a body 161 and a lid 160 laser welded togetherwith one of a welding pad or a stop projection on one or both of thework pieces. The shape of the housing varies and depends upon theexternal device that carries or contains the printhead, the amount ofink to be contained in the printhead and whether the printhead containsone or more varieties of ink. In any embodiment, the housing has atleast one compartment, internal thereto, for holding an initial orrefillable supply of ink and a structure, such as a foam insert, lung orother, for maintaining appropriate backpressure in the inkjet printheadduring use. In one embodiment, the internal compartment includes threechambers for containing three supplies of ink, especially cyan, magentaand yellow ink. In other embodiments, the compartment may contain blackink, photo-ink and/or plurals of cyan, magenta or yellow ink. It will beappreciated that fluid connections (not shown) may exist to connect thecompartment(s) to a remote source of ink.

A portion 191 of a tape automated bond (TAB) circuit 201 adheres to onesurface 181 of the housing while another portion 211 adheres to anothersurface 221. As shown, the two surfaces 181, 221 exist perpendicularlyto one another about an edge 231.

The TAB circuit 201 has a plurality of input/output (I/O) connectors 241fabricated thereon for electrically connecting a heater chip 251 to anexternal device, such as a printer, fax machine, copier, photo-printer,plotter, all-in-one, etc., during use. Pluralities of electricalconductors 261 exist on the TAB circuit 201 to electrically connect andshort the I/O connectors 241 to the bond pads 281 of the heater chip 251and various manufacturing techniques are known for facilitating suchconnections. It will be appreciated that while eight I/O connectors 241,eight electrical conductors 261 and eight bond pads 281 are shown, anynumber are embraced herein. It is also to be appreciated that suchnumber of connectors, conductors and bond pads may not be equal to oneanother.

The heater chip 251 contains at least one ink via 321 that fluidlyconnects to a supply of ink internal to the housing. During printheadmanufacturing, the heater chip 251 preferably attaches to the housingwith any of a variety of adhesives, epoxies, etc. well known in the art.As shown, the heater chip contains four rows (rows A-row D) of heaters.For simplicity in this crowded figure, dots depict the heaters in therows. It will be appreciated that the heaters of the heater chippreferably become formed as a series of thin film layers made viagrowth, deposition, masking, photolithography and/or etching or otherprocessing steps. A nozzle plate with pluralities of nozzle holes, notshown, adheres over the heater chip such that the nozzle holes alignwith the heaters.

With reference to FIG. 8, an external device, in the form of an inkjetprinter, for containing the printhead 101 is shown generally as 401. Theprinter 401 includes a carriage 421 having a plurality of slots 441 forcontaining one or more printheads. The carriage 421 is caused toreciprocate (via an output 591 of a controller 571) along a shaft 481above a print zone 431 by a motive force supplied to a drive belt 501 asis well known in the art. The reciprocation of the carriage 421 isperformed relative to a print medium, such as a sheet of paper 521, thatis advanced in the printer 401 along a paper path from an input tray541, through the print zone 431, to an output fray 561.

In the print zone, the carriage 421 reciprocates in the ReciprocatingDirection generally perpendicularly to the paper Advance Direction asshown by the arrows. Ink drops from the printheads are caused to beejected from the heater chip 251 (FIG. 7) at such times pursuant tocommands of a printer microprocessor or other controller 571. The timingof the ink drop emissions corresponds to a pattern of pixels of theimage being printed. Often times, such patterns are generated in deviceselectrically connected to the controller (via Ext. input) that areexternal to the printer such as a computer, a scanner, a camera, avisual display unit, a personal data assistant, or other.

To print or emit a single drop of ink, the heaters (the dots of rowsA-D, FIG. 7) are uniquely addressed with a small amount of current torapidly heat a small volume of ink. This causes the ink to vaporize in alocal ink chamber and be ejected through, and projected by, a nozzleplate towards the print medium.

A control panel 581 having user selection interface 601 may also provideinput 621 to the controller 571 to enable additional printercapabilities and robustness.

As described herein, all embodiments have included a first work pieceembodied as a laser light transparent material and a second work pieceembodied as a laser light absorbing material. The transparency oropaqueness of these structures, however, does not mean that 100% laserlight gets transmitted or blocked. The transparency and opacity is onlyrequired to allow enough light to transit the first work piece and getabsorbed by the second work piece to form an appropriate laser weld. Apreferred satisfactory rate of transmission for the first work pieceincludes rates above about 50%. A more preferred rate includes ratesabove about 80%. Those skilled in the art know that numerous parameterscontribute to the rate of transmission and include, among others, laserwavelength, incident angle of the laser beam, surface roughness of thework piece, temperature of the work pieces, thickness/dimensions of thework piece, composition of the work piece and, in the instance when thework pieces comprise plastics, additives such as flame retardants,plasticizers, fillers and colorants.

With reference to FIG. 9, since mono ink and color ink inkjet printheadbodies have different internal surfaces which causes welding to occur atdifferent locations and since a manufacturer would suffer inconvenienceif required to retool a laser welding apparatus when switchingmanufacturing from mono to color bodies, the invention further disclosesmethods of selectively controlling laser light according to whether theinkjet printhead body embodies a mono or color ink type. In FIG. 9A, theinkjet printhead body type embodies a mono ink cartridge having aperimeter 920 to-be-welded surface while in FIG. 9B it embodies a colorink cartridge having a perimeter 920 plus interior 940 to-be-weldedsurface. In particular, the interior has a T-shape that separates threesubstantially equal volume ink container sections 960 whereas the monoink embodiment has a single container section 921.

In FIG. 10A, pluralities of laser beam fiber optic bundles 1002 willbecome controlled such that light will pass through the fiber opticbundles and illuminate an inkjet printhead lid to weld in a pattern,generally 1010, substantially similar to the perimeter 920 to-be-weldedsurface. In FIG. 10B, pluralities of laser beam fiber optic bundles 1004will become controlled such that light will pass through the fiber opticbundles and illuminate an inkjet printhead lid to weld in a pattern,generally 1020, plus pattern 1010 together yielding a composite patternsubstantially similar to the perimeter 920 plus interior 940to-be-welded surface.

Representative laser welding structures that can accomplish the patterncontrol of FIGS. 10A, 10B are shown in FIGS. 11A and 11B. Specifically,either one laser light source 1110 having two discrete lines of control1112 a, 1112 b, or two light sources 1116 a, 1116 b each having a uniquecontrol line 1118 a, 1118 b, become controlled such that either thelaser beam fiber optic bundles 1002 or the laser beam fiber opticbundles 1002 together with the laserbeam fiber optic bundles 1004illuminate an inkjet printhead lid 1120, to weld to an inkjet printheadbody 1130, in either a pattern substantially similar to the perimeterto-be-welded surface or the perimeter plus interior to-be-weldedsurface.

The housing 1140 that contains the pluralities of laser beam fiber opticbundles may raise (arrow A) or lower (arrow B) onto an upper surface1121 of the inkjet printhead to release or supply a pressing engagementof the lid and body.

In one embodiment, the laser source represents an 810 nm wavelengthAluminum Gallium Arsenide (AlGaAs) semiconductor laser having a laserpower of about 50 watts. Other embodiments include, but are not limitedto, other types of continuous wave lasers with similar power intensitysuch as semiconductor lasers based on Indium Gallium Arsenide (InGaAs)with wavelengths 940-990 nm and Aluminum Gallium Indium Phosphide(AlGaInP) with wavelengths 630-680 nm, solid state lasers such as lamppumped Neodymium-doped Yttrium Aluminum Garnet (Nd:YAG) with wavelength1064 nm and diode pumped Neodymium-doped Yttrium Aluminum Garnet(Nd:YAG) with wavelength 1064 nm or other.

Consequently, a single laser welding structure can shuttle varieties ofinkjet body types through the structure and weld each type withouthaving to retool its basic configuration. As an example, an inkjetprinthead lid welds to a mono inkjet printhead body with a perimeterto-be-welded surface by illuminating the inkjet printhead lid 1120 withpluralities of laser beam fiber optic bundles 1002 in a pattern 1010substantially similar to the perimeter to-be-welded surface. Thereafter,the welded inkjet printhead lid gets exchanged for another inkjetprinthead lid requiring welding to a color inkjet printhead body with aperimeter plus interior to-be-welded surface and becomes illuminated,through control of the laser light source(s), with pluralities of laserbeam fiber optic bundles 1002 and 1004 in a composite pattern 1020 pluspattern 1010 together being substantially similar to the perimeter plusinterior to-be-welded surface of FIG. 9B.

Those skilled in the art, however, should appreciate that this inventionhas utility beyond the patterns shown and may extend to any pattern,line, shape or other.

The foregoing description is presented for purposes of illustration anddescription of the various aspects of the invention. The descriptionsare not intended to be exhaustive or to limit the invention to theprecise form disclosed. For example, the written specificationconsistently used a first work piece as embodying a laser transparentwork piece while the second work piece embodied a laser light absorbentwork piece. In the claims, however, the first and second work pieces canbe either transparent, light absorbing or having portions of bothtransparency or light absorbency and are only limited if specificallyrequired to be transparent or absorbent. Still further, the embodimentsdescribed above were chosen to provide the best illustration of theprinciples of the invention and its practical application to therebyenable one of ordinary skill in the art to utilize the invention invarious embodiments and with various modifications as are suited to theparticular use contemplated. All such modifications and variations arewithin the scope of the invention as determined by the appended claimswhen interpreted in accordance with the breadth to which they arefairly, legally and equitably entitled.

1. An inkjet printhead, comprising: a lid transparent to laser light; abody that is laser light absorbent; and a welding pad having a volumeprior to welding located on one of the lid and body, whereby saidwelding pad is laser welded at a weld interface to a surface of theother of the lid and body to substantially prevent bowing of a weldjoint at the weld interface.
 2. The inkjet printhead of claim 1, whereinthe welding pad is integrally formed on one of the lid and body.
 3. Theinkjet printhead of claim 1, wherein prior to welding the welding padhas a height, width, and length, such that the height is less than thewidth and the length is substantially equal to a length of one of thelid and body.
 4. The inkjet printhead of claim 1, wherein more than onewelding pad exists on one of the lid and body.
 5. The inkjet printheadof claim 4, wherein a horizontal distance exists between at least one ofthe more than one welding pad and another one of the more than onewelding pad.
 6. The inkjet printhead of claim 1, wherein the lid has afirst welding pad and the body has a second welding pad.
 7. The inkjetprinthead of claim 6, wherein the first and second welding pad each havea side surface that exist adjacent to one another when contacted.
 8. Theinkjet printhead of claim 6, wherein the second welding pad has asurface that exists substantially flush with a surface of the body. 9.The inkjet printhead of claim 6, wherein the first welding pad exists ata terminal end of the lid.
 10. The inkjet printhead of claim 6, whereinthe first welding pad does not exist at a terminal end of the lid. 11.The inkjet printhead of claim 1, wherein the lid is configured totransmit laser light at a rate of above 50%.
 12. The inkjet printhead ofclaim 1, wherein the lid comprises a material selected from the groupconsisting of polyphenylene ether, polystyrene, copolyesters,polyethylene terephthalate, glycol modified polyethylene terephthalate,glycol modified polycyclohexylenemethylene terephthalate, polybutyleneterephthalate, acid modified polycyclohexylenemethylene terephthalate,styrene methyl methacrylate, styrene acrylonitrile, acrylonitrilebutadiene styrene, methacrylate acrylonitrile butadiene styrene, andcompositions thereof.
 13. The inkjet printhead of claim 1, wherein thebody comprises a material selected from the group consisting ofpolystyrene, styrene-butadiene copolymers, styrene-acrylic copolymers,polyesters, polyethylene terephthalate, polybutylene terephthalate,polycarbonate, acrylonitrile styrene acrylic, and compositions thereof.14. An inkjet printhead, comprising: a lid transparent to laser light; abody that is laser light absorbent; a welding pad having a volume priorto welding located on one of the lid and body; and a stop projectionlocated on one of the lid and body contacting a surface of the other ofthe lid and body, whereby said welding pad is laser welded at a weldinterface to a surface of the other of the lid and body to substantiallyprevent bowing of a weld joint at the weld interface and said stopprojection existing at a separation distance from the weld interface tocontrol a distance of collapse at the weld interface between said lidand said body.
 15. The inkjet printhead of claim 14, wherein a bufferexists between the weld interface and the stop projection.